The value attribute in HTML and the value property in JavaScript work differently for these controls.
You can set the initial value with the value attribute, but the value property contains
the actual value of the control. If you want to get or set the initial value in JavaScript, use the defaultValue property.

For the input:checkbox and the input:radio elements, the contents of the value property do not appear
in the user interface. For these two elements the value property only has meaning when submitting a form.
See the page for the input:checkbox and the input:radio elements for details.

Sometimes it is useful to check the contents of the controls in a form before submitting.
See the page for the form tag or the pages for the objects that support the value property for details
(you can see these objects in the 'Supported by objects' section below).